Near-confocal cavity-enhanced Raman spectroscopy for multitrace-gas detection.

Simultaneous detection of multitrace gas is still a challenge. Near-confocal cavity-enhanced Raman spectroscopy is proposed and demonstrated for simultaneous detection of multitrace gas. With a 200 mW incident laser, the excitation power of >9 W forms at two foci of the near-confocal cavity owing to the beam being reflected 50 times. High-power excitation light greatly enhances the detection sensitivity of the Raman system. Using this cavity-enhancing technique, high-sensitivity detection of the mixture of eight gases with same volume ratio has been achieved. This technique may be applied for detecting multitrace gas in many areas.